The Underwood hardcast packs a serious punch and doesn't deform. I bought a couple boxes earlier this year and tried them on various objects. My review of them after one such experiment is as follows: "I put some underwood 200gr hardcast through my XDm. I did great. They went through 3 2x4s and a 16 inch stump before stopping an inch or so into another stump. I feel confident in them." I dug the bullets out and they held their shape very well. I recently got some Extreme Penetrators and will be trying those out in the near future, likely with plate steel and reams of paper. There are enough ballistics gel videos on YouTube that I don't need to do that experiment. I expect it will be much the same as the hardcasts; a .40 cal hole drilled deep into the target with little expansion, unless the target is filled with water, then I expect the flutes to create a nasty wound. In either event, I expect deep penetration and no expansion.
As Hans said, hardcasts and rounds in the same category are great if you're worried about getting through heavy bone and muscle. If it's something like a wolf or a cougar you're worried about then a heavy hollowpoint has a better chance of causing the tissue damage you're looking for to stop the threat and less chance of just a .40 cal hole all the way through.
My two cents.